The present work was aimed at analysing the oxidation behaviour of three nickel-based superalloys-Superni 718, Superni 75 and Superni 750, by conducting in-situ study in the secondary chamber of a medical waste incinerator at 800–850°C for 1000 h. It was observed that among the three superalloys, Superni 75 is best suited for such an environment. This was concluded by comparing the weight change after 100 h for total 1000 h, constituting 10 thermal cycles. The morphology of the oxide scale formed on the substrate was analysedusing FE-SEM. The elemental composition was obtained by EDS. The depth profiling of the scale was done using the XPS technique. The chemical composition was also examined by the XRD analysis. The superior oxidation property of Superni 75 is due to the higher Ni-Cr content. The oxidation resistance of the nickel-based superalloys in the aggressive environment of medical waste incinerator is attributed to the presence of chromia oxide-Cr₂O₃ and spinel NiCr₂O₄.